Alternative activity of beta-lactam antibiotics against methicillin- and cephem-resistant Staphylococcus aureus in the presence of respiratory tract mucus.
Methicillin- and cephem-resistant Staphylococcus aureus (MRSA) strains were found to be unable to grow in sputum from patients treated with a beta-lactam antibiotic. Sputum containing no beta-lactams also exhibited bactericidal activity when the MRSA strain was pretreated with a subinhibitory concentration of a beta-lactam; however, lysozyme-free sputum was inactive. Peptidoglycan of MRSA grown in the presence of cefazolin was susceptible to lysis by respiratory mucus. Hen albumen lysozyme contained the same activity against beta-lactam-treated MRSA. The median minimum inhibitory concentration of cefazolin for 45 S. aureus strains (including 20 MRSA strains) shifted from approximately 50 micrograms/ml to approximately 0.78 microgram/ml by addition of 1 mg/ml of hen albumen lysozyme to susceptibility-testing media. Such lysozyme-dependent antistaphylococcal activity was manifested specifically with beta-lactams (9 penicillins, 10 cephalosporins, 3 cephamycins, 1 oxacephem, and 1 carbapenem).
Igarashi
K
K
Department of Medicine, Nigata University School of Medicine, Japan.
Matsuyama
T
T
D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002437:Cefazolin / Q000494:pharmacology; D003470:Culture Media; D004352:Drug Resistance, Microbial; D005260:Female; D006801:Humans; D008297:Male; D008712:Methicillin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009113:Muramidase; D010403:Penicillin Resistance; D013183:Sputum / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects*
D000900:Anti-Bacterial Agents; D003470:Culture Media; D009113:Muramidase; D002437:Cefazolin; D008712:Methicillin